/Engine/Plugins/Runtime/CommonUI/Source/CommonUI/Public/Input/CommonUIActionRouterBase.h
bool RegisterLinkedPreprocessor ( const [UWidget](API\Runtime\UMG\Components\UWidget) & Widget, const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [IInputProcessor](API\Runtime\Slate\Framework\Application\IInputProcessor) > & InputPreprocessor, int32 DesiredIndex )